Regenerative afterburner

ABSTRACT

A regenerative post-combustion apparatus ( 1 ) in a housing ( 2 ) in a known manner comprises from top to bottom a combustion chamber ( 8 ), a heat exchanger area ( 7 ) subdivided into a plurality of segments filled with heat exchanger material, and a rotating distributor ( 5 ). The latter depending on its rotational position establishes a connection, on the one hand, between an inlet ( 3 ) for waste gas to be cleaned and at least one first segment of the heat exchanger area ( 7 ), as well as between at least one second segment of the heat exchanger area ( 7 ) and an outlet ( 10 ) for cleaned gas. Disposed above the rotating distributor ( 5 ) is a burn-out rotary slide valve ( 31 ). The latter is subdivided by dividing walls into segments, of which one is closed in the direction of the rotating distributor ( 5 ) and communicates with an outlet ( 68 ). The other segments of the burn-out rotary slide valve ( 31 ) are open in a downward and an upward direction. The burn-out rotary slide valve ( 31 ) may be rotated in such a way that its downwardly closed segment may be brought selectively into communication with each of the segments of the heat exchanger area ( 7 ). In said segment, thermal regeneration of the heat exchanger material situated there occurs without the normal operation of waste gas cleaning having to be interrupted in the other segments.

The invention relates to a regenerative post-combustion apparatus, whichin a housing comprises from top to bottom:

a) a combustion chamber;

b) a heat exchanger area, which is subdivided into a plurality ofsegments filled with heat exchanger material;

c) a rotating distributor, which depending on its rotational positionestablishes:

ca) a connection between an inlet for waste gas to be cleaned and atleast one first segment of the heat exchanger area;

cb) a connection between at least one second segment of the heatexchanger area and an outlet for cleaned gas,

wherein a device for thermal regeneration of the heat exchanger materialis provided, by means of which hot clean gas may be conveyed throughselected segments of the heat exchanger area until the impurities, whichhave become attached to the heat exchanger material, detach from thelatter.

Regenerative post-combustion apparatuses are used to clean contaminatedwaste gases from industrial processes. To save energy during the thermalpost-combustion, the waste gases to be cleaned are conveyed through heatexchanger materials. As the waste gases to be cleaned frequently containimpurities, in particular also organic impurities in the form ofcondensable substances, e.g. tar products, or dusts, in the course ofoperation the surfaces of the heat exchanger materials become cloggedwith said impurities. For regeneration, the heat exchanger materialperiodically has to be heated up to a temperature, at which theimpurities attached to the surface detach themselves and may be removed.In the present context, by “attached” impurities are meant allimpurities which may attach to the heat exchanger material mechanically,chemically, through absorption, through adsorption or throughcondensation processes and may be removed by a thermal process combinedwith flow.

This occurs in the known thermal post-combustion apparatuses in thattheir normal operation, during which the waste gases are cleaned, isinterrupted. Hot gases, which may originate e.g. from the combustionchamber, are conveyed through the individual segments of the heatexchanger material until said segments have been heated from top tobottom up to the required temperature so that all regions of the heatexchanger material in said segments are freed of impurities. Thedrawback of said known regenerative post-combustion apparatuses is thatnormal operation has to be suspended for regeneration. Thus, if acontinuous cleaning operation is to be ensured, it is necessary toprovide, for the downtimes of the one regenerative post-combustionapparatus, a second post-combustion apparatus lying parallel thereto.

The object of the present invention is to refine a regenerativepost-combustion apparatus of the type described initially in such a waythat it enables a continuous cleaning operation also during thermalregeneration of the heat exchanger material.

Said object is achieved according to the invention in that the devicefor thermal regeneration comprises:

d) a burn-out rotary slide valve, which is disposed above the rotatingdistributor and comprises segments separated by dividing walls, wherein

da) at least one of the segments of the burn-out rotary slide valve isopen in an upward direction and closed in the direction of the rotatingdistributor and communicates with an outlet, while

db) the other segments of the burn-out rotary slide valve are open in anupward and downward direction;

e) a driving device, by means of which the burn-out slide valve may berotated in such a way underneath the heat exchanger area that itsdownwardly closed segment may be brought selectively into communicationwith each segment of the heat exchanger area.

In a post-combustion apparatus according to the invention, therefore,the gas flow from the rotating distributor into the segmented heatexchanger area filled with heat exchanger material is controlled by anadditional element, the “burn-out rotary slide valve”. The latter in noway alters the basic mode of operation as regards waste gas cleaningcompared to prior art; the only difference is that the flow path fromthe rotating distributor into the heat exchanger area is slightly longercompared to prior art. However, with the post-combustion apparatusaccording to the invention it is possible to remove an individualsegment or individual segments of the heat exchanger area from the wastegas cleaning operation. For said purpose, the burn-out rotary slidevalve is rotated in such a way that its downwardly closed segmentcommunicates with the segment or segments of the heat exchanger areawhich is/are to be thermally regenerated. The latter is/are then nolonger periodically cooled by a supply of cool outgoing air. It is orthey are then heated from top to bottom by the hot gas used for thermalregeneration, which is conveyed either from the combustion chamber ofthe regenerative post-combustion apparatus via the relevant segments ofthe heat exchanger area to be regenerated and via the downwardly closedsegment of the burn-out slide valve to the outlet or in the reversedirection. In either case the gases, which flow through the segments ofthe heat exchanger area to be regenerated and through the downwardlyclosed segment of the burn-out slide valve, are ultimately conveyed(once more) into the combustion chamber where the impurities, which havedetached from the heat exchanger material during the regenerationprocess, are burnt. Said operation may, where required, be carried outseparately for each segment of the heat exchanger area.

When the number of segments of the heat exchanger area corresponds tothe number of segments of the burn-out rotary slide valve, this meansthat there is always one of the segments of the heat exchanger areawhich is unable to participate in the waste gas cleaning operation. Thisis avoided in the particularly advantageous embodiment of the invention,in which the heat exchanger area is subdivided into n segments and

a) the burn-out rotary slide valve is subdivided into (n+1) segments, ofwhich n are open in an upward and downward direction and one is open inan upward direction and closed in a downward direction;

b) provided in the flow path between the burn-out rotary slide valve andthe heat exchanger area is a transfer area, which

ba) at its top side is subdivided into n sectors, which each enclose anangle of 360°/n and have a through-opening, which communicates with oneof the n segments of the heat exchanger area;

bb) at its bottom side is subdivided into (n+1) sectors, which eachenclose an angle of 360°/(n+1), wherein n of said sectors have athrough-opening, which depending on the rotational position of theburn-out rotary slide valve may communicate with each of the latter's(n+1) segments, while one sector is closed and in a specific rotationalposition of the burn-out rotary slide valve is positioned above thelatter's downwardly closed segment;

bc) has n dividing walls, which in part extend obliquely in such amanner from the top side to the bottom side of the transfer area thatthe latter is subdivided into n segments, which at the top and bottomside each have a through-opening, wherein at least one of said segmentsat its bottom side is delimited at least partially by the closed sector.

The fact, that in said embodiment of the invention the burn-out rotaryslide valve has one segment more than the heat exchanger area, allowsthe burn-out rotary slide valve to have just as many upwardly anddownwardly open segments, i.e. segments participating in the waste gascleaning operation, as the heat exchanger area. By virtue of the trickof the so-called “transfer area” the transition is provided between thesegment arrangement, such as the heat exchanger area has, and thesegment arrangement provided in the burn-out rotary slide valve. Thetransfer area at its bottom side with the closed sector provides asurface, under which the downwardly closed segment of the burn-outrotary slide valve may be “parked” when there is to be no thermalregeneration in any segment of the heat exchanger area.

It is advantageous when the burn-out rotary slide valve comprises acentral tubular piece, the interior of which communicates via an openingin its lateral surface with the downwardly closed segment of theburn-out rotary slide valve. The hot gas used for thermal regenerationis in said case supplied to, or discharged from, the burn-out rotaryslide valve via the central tubular piece.

The central tubular piece of the burn-out rotary slide valve may beclosed in a downward direction and communicate at the top with a coaxialcentral tubular piece of the above-lying component, which communicateswith the connection. This means that the hot gas used for thermalregeneration is supplied from above to the burn-out rotary slide valveand discharged from the latter in an upward direction.

Alternatively, it is also possible for the central tubular piece of theburn-out rotary slide valve to be closed in an upward direction andcommunicate at the bottom with a coaxial central tubular piece of thecomponent below, which communicates with the connection.

Which of the two latterly described embodiments of the invention is usedwill depend upon the geometric proportions of each individual case.

A further possibility of conveying the hot gas used for thermalregeneration through the burn-out rotary slide valve is such that thedownwardly closed segment of the burn-out rotary slide valve has in itslateral surface an opening, via which it communicates with a stationaryannular channel, which surrounds the burn-out rotary slide valve and inturn communicates with the connection. In said refinement of theinvention, the hot gas used for thermal regeneration is supplied to, anddischarged from, the burn-out rotary slide valve radially, which inindividual cases is preferable likewise for geometric reasons.

Embodiments of the invention are described in detail below withreference to the drawings; the drawings show:

FIG. 1 a diagrammatic vertical section through a regenerativepost-combustion apparatus with the most important peripheral equipmentneeded for its operation;

FIG. 2 a partial enlargement from FIG. 1;

FIG. 3 a diagrammatic isometric view of the transfer area of thepost-combustion apparatus of FIG. 1;

FIG. 4 a diagrammatic isometric view of the burn-out rotary slide valveof the post-combustion apparatus of FIG. 1;

FIG. 5 the plan view of the bottom plate of the transfer area of FIG. 3;

FIG. 6 the plan view of the top plate of the transfer area of FIG. 3;

FIG. 7 the plan view of the bottom plate of the burn-out rotary slidevalve of FIG. 4;

FIG. 8 the plan view of the top plate of the burnout rotary slide valveof FIG. 4;

FIG. 9 the plan view of the rotary slide valve of the post-combustionapparatus of FIG. 1;

FIGS. 10 and 11 the post-combustion apparatus of FIG. 1 but in each casewith different routes of the gas used for thermal regeneration;

FIG. 12 an alternative embodiment of a regenerative post-combustionapparatus with peripheral equipment according to FIG. 1;

FIG. 13 a partial enlargement from FIG. 12;

FIGS. 14 and 15 the post-combustion apparatus of FIG. 12 but in eachcase with different routes of the gas used for thermal post-combustion;

FIG. 16 a third embodiment of a regenerative post-combustion apparatuswith the most important peripheral equipment;

FIG. 17 a partial enlargement from FIG. 1;

FIGS. 18 and 19 the post-combustion apparatus of FIG. 16 but in eachcase with different routes of the gas used for thermal regeneration.

In FIG. 1 the regenerative post-combustion apparatus is denoted as awhole by the reference character 1. Its basic construction and its basicmode of operation are—unless otherwise indicated below—described in EP 0548 630 A1 or EP 0 719 984 A2, to which express reference is made.

Situated in the bottom region of the housing 2 of the regenerativepost-combustion apparatus 1 is an inlet 3 for the outgoing air, which isto be cleaned and is supplied via the inlet line 4. Said gas passes intoa plenum chamber 30, in which it flows axially—in relation to the axisof the housing 2—upwards. Through bellow expansion joints 40, which takeup different degrees of thermal expansion, the gas passes into arotating distributor 5, which may be set in continuous or intermittentrotation by means of a drive, which is not shown in FIG. 1.

The rotating distributor 5, depending on its rotational position,establishes a connection between the inlet 3 and one or more segments ofa plurality of pie segments in a distribution area 6 situated in themiddle region of the housing 2. The gases, on their way from therotating distributor 5 to the various segments of the distribution area6, additionally pass through a burn-out rotary slide valve 31, which maylikewise be intermittently set in rotation in a non-illustrated manner,as well as a stationary transfer area 41; the precise design andfunction of burn-out rotary slide valve 31 and transfer area 41 aredescribed in detail further below.

Situated above the distribution area 6 in the housing 2 is a heatexchanger area 7, which is subdivided into a corresponding number ofsegments, which communicate in each case with a corresponding segment ofthe distribution area 6 below. The segments of the heat exchanger area 7are filled with heat exchanger material.

Situated above the heat exchanger area 7 in the uppermost region of thehousing 2 is a combustion chamber 8, opening into which is a burner 9.

Said rough summary of the design of the post-combustion apparatus 1 isnow followed by a detailed description of the components which are ofmost importance in the present context, namely the rotary slide valve 5,the burn-out rotary slide valve 31, the transfer area 41 and theassociated internal and external lines. Here, for descriptive purposesan embodiment of the post-combustion apparatus 1 is selected, in whichthe heat exchanger area 7 is subdivided by radially extending dividingwalls into eleven segments of equal size, i.e. each two adjacentdividing walls enclose an angle of around 32.7°. The distribution area 6situated below is segmented in the same manner and therefore likewisecomprises eleven segments of equal size, which communicate via openings25 (cf. FIG. 2) in the dividing wall 42 between heat exchanger area 7and distribution area 6 with the corresponding segments of the heatexchanger area 7.

The dividing wall 43, which closes off the distribution area 6 in adownward direction, is provided in the central region of each segmentwith an opening 26 cf. FIG. 2). Below said openings 26 the transfer area41 illustrated in FIG. 3 is fastened. For a detailed description of thelatter, reference is now made to FIGS. 3, 5 and 6.

The transfer area 41 is delimited by a top plate 44, a bottom plate 45and a cylindrical lateral surface 46. In FIG. 3 top plate 44, bottomplate 45 and cylindrical lateral surface 46 are shown onlydiagrammatically by dashed outlines in order to afford a view into theinterior of the transfer area 41.

The top plate 44 of the transfer area 41 shown in plan view in FIG. 6 isprovided with eleven pie-segment-shaped holes 47 of equal size, betweenwhich lie strip-shaped intermediate areas 50. Each hole 47 communicateswith an above-lying segment of the distribution area 6 via an opening 26in the dividing wall 43. Situated in the centre of the plate 44 is acircular opening 27.

The bottom plate 45 of the transfer area 41 shown in FIG. 5, on theother hand, is subdivided into twelve sectors, which enclose in eachcase an angle of 30°. Of said twelve sectors, eleven are provided with acorresponding pie-segment-shaped hole 48 and strip-shaped intermediateareas 51 lie between said holes. The twelfth sector 49 is closed.Situated in the centre of the plate 45 is a circular opening 28.

Between the eleven holes 47 in the top plate 44 and the eleven holes 48in the bottom plate 45 of the transfer area 41 eleven segment-likeconnections are then created by eleven dividing walls 49 in thefollowing manner:

Ten of the eleven dividing walls 49 extend axially from the strip-shapedintermediate areas 50 of the top plate 44 to corresponding strip-shapedintermediate areas 51 of the bottom plate 45. The twelfth dividing wall49 extends from the remaining strip-shaped intermediate area 50 of thetop plate 44 to the centre line of the closed sector 41 of the bottomplate 45, as may be seen from FIG. 3. Since, as mentioned, the holes 47of the top plate 44 enclose a greater angle than the holes 48 of thebottom plate 45, the dividing walls 49 extend for the most part not inan axial plane but are set obliquely towards the axis of the transferarea 45.

In radial direction the dividing walls 49 of the transfer area 41 extendfrom the latter's lateral surface 46 to a central tubular piece 65,which connects the circular opening 28 in the bottom plate 45 to thecircular opening 27 in the top plate 44 and hence creates an axialpassage through the transfer area 41.

The purpose of the transfer area 41 is to provide at its bottom plate 45not only eleven pie-segment-shaped holes 48, which communicate with thecorresponding eleven segments of the air distribution area 6 of the heatexchanger area 7, but also a closed sector surface 41, the purpose ofwhich will be disclosed in the interaction with the burn-out rotaryslide valve 31 described below.

The burn-out rotary slide valve 31 is illustrated in FIGS. 4, 7 and 8.It is delimited by a top plate 52, a bottom plate 53 and a cylindricallateral surface 54. Top plate 52, bottom plate 53 and cylindricallateral surface 54 are likewise shown only as dashed outlines in FIG. 4in order to afford a view into the interior of the burn-out rotary slidevalve 31.

The top plate 52 of the burn-out rotary slide valve 31 shown in FIG. 8comprises twelve pie-segment-shaped apertures 55 of equal size, whichtherefore enclose in each case an angle of 30° and are separated bystrip-shaped intermediate areas 56. In the centre the top plate 52 has acircular opening 57.

The bottom plate 53 of the burn-out rotary slide valve 31 shown in FIG.7 is divided into 12 sectors of equal size, of which 11 are providedwith pie-segment-shaped holes 58. The pie-segment-shaped holes 58 areseparated from one another by strip-shaped intermediate areas 59. Thetwelfth sector 60 of the bottom plate 53 is closed. In the centre thebottom plate 53 of the burn-out rotary slide valve 31 has a circularhole 61.

As is evident from FIG. 4, a central tubular piece 62 extends axiallyfrom the circular opening 57 in the top plate 52 to the circular opening61 in the bottom plate 53. Extending radially between the tubular piece62 and the cylindrical lateral surface 54 are twelve dividing walls 63,which extend axially in each case from the strip-shaped intermediateareas 56 of the top plate 52 to the strip-shaped intermediate areas 59of the bottom plate 53 and/or to the edges of the closed sector 60. Thisgives rise in the burn-out rotary slide valve 31 to twelve segments, ofwhich one is blocked in a downward direction by the closed sector 60while a passage is formed from top to bottom through the remainingeleven.

The tubular piece 62 of the burn-out rotary slide valve 31 is incommunication via a radial opening 64 with the interior of the segmentwhich is closed in a downward direction.

The rotating distributor 5 disposed underneath the burn-out rotary slidevalve 31 is of a construction which is known as such. Depending on itsrotational position, it establishes a connection between the plenumchamber 30 and specific segments in the burn-out rotary slide valve 31and hence also specific segments of the transfer area 41, thedistribution area 6 and the heat exchanger area 7. It moreover connectsspecific further segments of the burn-out rotary slide valve 31, whichgenerally lie diametrically opposite the first-mentioned segments, andhence also further segments of the heat exchanger area 7, thedistribution area 6 and the transfer area 41 to an outlet 10 (cf.FIG. 1) for cleaned gas. Finally, the rotating distributor 5 via theburn-out rotary slide valve 31 and the transfer area 41 establishes aconnection between the segment of the distribution area 6, and hence ofthe heat exchanger area 7, which viewed in the direction of rotation ofthe rotating distributor 5 is in advance of the segments communicatingwith the outlet 10, and a scavenging air inlet 11 (cf. FIG. 1).

To enable the described connections to be established, the rotatingdistributor 5 comprises various apertures, of which the mouths into thetop end of the rotating distributor 5 are diagrammatically illustratedin FIG. 9. The direction of rotation of the rotating distributor 5 isdenoted by the arrow 32. The aperture for the outgoing air to be cleanedis denoted by the reference character 33, the aperture for thescavenging air by the reference character 34 and the aperture for thecleaned air by the reference character 35. Remaining between the variousapertures 33, 34, 35 are closed, pie-segment-shaped regions 36, 37, 38of the top end face of the rotating distributor 5, which enclose in eachcase an angle of 30°.

The central tubular piece 65 of the transfer area 41 (cf. FIGS. 1 to 3)is lengthened coaxially by a tubular piece 66, which extends axiallythrough the distribution area 6. Branching off at right angles from thelatter tubular piece is a further tubular piece 67, which passesradially through the distribution area 6, penetrates the shell of thehousing 2 and terminates at a gas connection 68. As FIG. 1 reveals, thegas connection 68 is connected by a line 69 containing a blower 70 to aninlet 71, which is disposed at the top region of the housing 2 and leadsto the combustion chamber 8.

A line 72 leads from the outlet 10 for cleaned gas via a blower 73 tothe chimney no longer shown in the drawings, optionally via furtherintermediate treatment stations. Branching off from the line 72downstream of the blower 73 is a line 74, which is connected to thescavenging air inlet 11.

The described regenerative post-combustion apparatus 1 operates asfollows:

“Normal operation” in the following is to be understood as the mode ofoperation, in which in a known manner the contaminated waste gasessupplied via the line 4 are afterburnt in the combustion chamber 8 and,after an exchange of heat in the various segments of the heat exchangerarea 7, are discharged via the gas outlet 10 and the line 72 to thechimney. During said “normal operation” the burn-out rotary slide valve31 is situated in such a relative position underneath the transfer area41 that its segment, which is closed at the bottom by the sector 60,comes to lie below the closed sector surface 49 of the transfer area 41.In said position, therefore, the downwardly closed segment of theburn-out rotary slide valve 31 communicates neither axially in adownward direction nor axially in an upward direction. Thus, no gas atall flows via the opening 64, the interior of the tubular piece 62 ofthe burn-out rotary slide valve 31, the interior of the tubular piece 65of the transfer area 41 and the tubular pieces 66 and 67 in thedistribution area 6 in an outward direction to or from the gasconnection 68.

The rotating distributor 5 rotates underneath the burn-out rotary slidevalve 31 usually either continuously or intermittently from segment tosegment, wherein sequentially the waste gas to be cleaned is conveyed inaccordance with the position of the aperture 33 in the rotatingdistributor 5 into the corresponding segments of the burn-out rotaryslide valve 31, the transfer area 41, the distribution area 6 and theheat exchanger area 7 and into the combustion chamber 8. There, thegases are afterburnt in a known manner and then returned through thesegments of the heat exchanger area 7, the distribution area 6, thetransfer area 41 and the burn-out rotary slide valve 31 whichcommunicate with the aperture 34 of the rotating distributor 5. Fromthere, the now cleaned waste gases then pass through the outlet 10,having been drawn off by the blower 73, via the line 72 to the chimney.

Some of the cleaned gases is returned via the line 74 to the scavengingair inlet 11 and from there is introduced via an angled line 12, whichextends first through the plenum chamber 30 and then centrally in axialdirection through the bellow expansion joints 40, along a path (notshown in the drawings) into the segment of the rotating distributor 5corresponding to the scavenging air aperture 34. Said air then flows toa segment of the transfer area 41, the distribution area 6 and the heatexchanger area 7. The heat exchanger material contained in said segmentof the heat exchanger area 7 is swept by the cleaned pure air, whichremoves residues of the waste gas, which previously flowed through therelevant segment of the heat exchanger area 7, and passes into thecombustion chamber 8 where it is afterburnt again.

It is clear that the described “normal operation” of the regenerativepost-combustion apparatus 1 in no way differs from that of knownpost-combustion devices. A minor difference is that the effective freeflow area for the gases is always slightly reduced when one of theapertures 33, 34, 35 of the rotating distributor 5 overlaps the segmentof the burn-out rotary slide valve 31 which is blocked by the closedsector 60. Since, even in said case, the flow areas are stillsufficiently large, there are no further repercussions on the cleaningof the waste gases.

“Regenerative operation” in the following is to be understood as themode of operation, in which—besides the ongoing cleaning of wastegases—a specific segment inside the heat exchanger area 7 isadditionally thermally regenerated. For said purpose, the burn-outrotary slide valve 31 is moved out of the described position, in whichthe downwardly closed segment is “parked” below the sector region 41 ofthe transfer area 41, into a position below the opening 48 of thetransfer area 41 which communicates with the segment of the heatexchanger area 7 to be regenerated.

Said segment is then excluded from the normal process of being swept bywaste gas to be cleaned and/or by pure gas. Instead, hot gas from thecombustion chamber 8 is sucked through the relevant segment of the heatexchanger area 7 and flows through the corresponding segments of thedistribution area 6, the transfer area 41 and the downwardly closedsegment of the burn-out rotary slide valve 31 into the interior of thecentral tubular piece 62 of the burn-out rotary slide valve 31 and fromthere via the central tubular piece 65 of the transfer area 41, thetubular pieces 66 and 67 in the distribution chamber 6 to the gas outlet68. Via the line 69 said gases are conveyed with the aid of the blower70 to the inlet 71 and hence back into the combustion chamber 8, whereafterburning occurs.

The described circulation of the air through the segment of the heatexchanger area 7 to be regenerated continues until all impurities havebeen removed from the heat exchanger material of said segment.Afterwards—depending on requirements—the burn-out rotary slide valve 31may be rotated into a position below another hole 48 of the transferarea 41 associated with another segment of the heat exchanger area 7 tobe regenerated. In said manner, all of the segments of the heatexchanger area 7 in succession may be thermally regenerated withoutinterrupting the cleaning operation of the regenerative post-combustionapparatus 1; the latter continues to operate in parallel, albeit with aslightly reduced capacity because the segment of the heat exchanger area7 in the process of being regenerated does not participate in thecleaning operation.

Once impurities have been removed from all segments of the heatexchanger area 7 in said manner, the burn-out rotary slide valve 31 ismoved back into its “parking position”, in which its segment closed in adownward direction by the sector 60 lies below the closed sector 41 ofthe transfer area 41.

The flow direction of the gas which effects thermal regeneration of theheat exchanger material in the heat exchanger area 7 may alternativelybe reversed in comparison to the arrangement shown in FIG. 1. This isdiagrammatically illustrated in FIG. 10. The post-combustion apparatus 1is unaltered compared to FIG. 1. However, instead of the gas used forthermal regeneration being sucked out of the combustion chamber 8directly into the heat exchanger area 7, it is removed from thecombustion chamber 8 via a lateral outlet 14. The hot combustion gas isconveyed via a line 15, which contains a butterfly control valve 16 anda blower 17, to the gas connection 68. To adjust the correcttemperature, fresh air is introduced from the outside atmosphere via afurther butterfly control valve 18 into the line 15 and is added to thehot gas leaving the combustion chamber 8.

The path, which said gas subsequently follows from the gas connection68, is then the opposite of the flow path described above with referenceto FIG. 1. The segments of the heat exchanger area 7 are in said case,unlike in the embodiment of FIG. 1, swept from the bottom up. This hasthe advantage that the hot gases first reach the bottom regions of theheat exchanger material remote from the combustion chamber 8. In saidmanner, a homogeneous temperature required for detachment of theimpurities may be attained more.easily and more rapidly in the heatexchanger material. The gases emerging from the top of the heatexchanger area 7 and laden with impurities detached from the heatexchanger material are afterburnt jointly with the waste gas, which issituated in the normal cleaning process, in the combustion chamber 8.

Whereas in the embodiments illustrated in FIGS. 1 to 10 the gas used forthermal regeneration of the heat exchanger material was heated in thecombustion chamber 8, in the embodiment of FIG. 11 the gas is heated bya separate burner 19, to which fresh air is supplied with the aid of ablower 20 via a line 21. The path, which the thus heated gassubsequently follows from the gas connection 68 inside the regenerativepost-combustion apparatus 1, which is otherwise identical to that ofFIGS. 1 and 10, is the same as in FIG. 10.

FIG. 12 shows an axial section through a second embodiment of aregenerative post-combustion apparatus, which is very similar to that ofFIG. 1. Identical parts are therefore denoted by the same referencecharacters as in FIG. 1, plus 100.

The regenerative post-combustion apparatus 101 of FIG. 12 differs fromthat of FIG. 1 exclusively in the manner in which the gas used forthermal regeneration is conveyed in the region of the burn-out rotaryslide valve 131. Whereas in the embodiment of FIG. 1, as mentionedabove, the segment of the burn-out rotary slide valve 31 which is closedin a downward direction by the sector 60 was open radially in towardsthe central tubular piece 62, in the embodiment of FIG. 12 there is noconnection in said direction, as is particularly evident also from thepartial enlargement of FIG. 13. Instead, the relevant segment is open ina radially outward direction; the cylindrical lateral surface 154 of theburn-out rotary slide valve 131 therefore has at said point an opening121. The burn-out rotary slide valve 31 is surrounded by an annularchannel 122, which is rigidly fastened to the housing 102 and/or thedividing plate 143 at the underside of the distribution area 106. Atubular piece 167 connects the annular channel 122 to the gas connection168 at the outside of the housing 102.

Said design change leads to a slight modification of the flow path ofthe hot air used for thermal regeneration. In the arrangement of theperipheral equipment, which is selected in FIG. 12 and corresponds tothat of FIG. 1, said gas flows out of the downwardly closed segment ofthe burn-out rotary slide valve 31 radially outwards into the annularchannel 122 and from there via the tubular piece 167, the gas connection168 in the already previously described manner to the line 169 and viathe blower 170 to the gas inlet 171.

In the thermal post-combustion apparatus 101 of FIG. 12 said gas routemay be reversed in the same manner as is illustrated in FIG. 10 for thefirst described embodiment of a thermal post-combustion apparatus 1.This is shown in FIG. 14. It is naturally also possible in the thermalpost-combustion apparatus 102, as in the FIG. 11 discussed above, forthe air used for thermal regeneration to be removed directly from theoutside atmosphere and supplied via a blower 120 and a burner 119 to thegas inlet 168. This is illustrated in FIG. 15.

FIGS. 16 and 17 show a third embodiment of a thermal post-combustionapparatus, which again bears a close similarity to the embodiment ofFIG. 1. Identical parts are therefore provided with the same referencecharacters, plus 200. Again, the only difference is the route of the gasused for thermal regeneration in the region of the burn-out rotary slidevalve 131. Whereas, in the embodiment first described, the interior ofthe central tubular piece 62 of the burn-out rotary slide valve 31communicated with the above-lying central tubular piece 65 of thetransfer area 41, in the embodiment of FIGS. 16 and 17 the centraltubular piece 262 of the burn-out rotary slide valve 231 is closed in anupward direction and open in a downward direction. It communicates,here, with a pipe 229, which extends coaxially with the housing 2 and insections also coaxially with the scavenging air line 212 through thebellow expansion joints 240 to the underside of the housing 202. There,a line 267 branches off at right angles and leads radially outwards to agas connection 268.

The gas connection 268 is connected in the same manner as in FIGS. 1 and12 via a blower 270, which lies in a line 269, to the top inlet 271 ofthe thermal post-combustion apparatus 201.

FIG. 18 shows a route of the gas used for thermal regeneration whichcorresponds to that in the FIGS. 10 and 14 described above; FIG. 19shows the use of air, which is removed from the outside atmosphere andheated in a separate burner 219, in accordance with FIGS. 11 and 15, towhich reference is made.

What is claimed is:
 1. A regenerative post-combustion apparatus, whichin a housing comprises from top to bottom: a) a combustion chamber; b) aheat exchanger area, which is subdivided into a plurality of segmentsfilled with heat exchanger material; c) a rotating distributor, whichdepending on its rotational position establishes: ca) a connectionbetween an inlet for waste gas to be cleaned and at least one firstsegment of the heat exchanger area; cb) a connection between at leastone second segment of the heat exchanger area and an outlet for cleanedgas, wherein a device for thermal regeneration of the heat exchangermaterial is provided, by means of which hot clean gas may be conveyedthrough selected segments of the heat exchanger area until theimpurities, which have become attached to the heat exchanger material,detach from the latter; wherein the device for thermal regenerationcomprises: d) a burn-out rotary slide valve (31; 131; 231), which isdisposed above the rotating distributor (5; 105; 205) and comprisessegments separated by dividing walls (63), wherein da) at least one ofthe segments of the burn-out rotary slide valve (31; 131; 231) is openin an upward direction and closed in the direction of the rotatingdistributor (5; 105; 205) and communicates with an outlet (68; 168;268), while db) the other segments of the burn-out rotary slide valve(31; 131; 231) are open in an upward and downward direction; e) adriving device, by means of which the burn-out slide valve (31; 131;231) may be rotated in such a way underneath the heat exchanger area (7;107; 207) that its downwardly closed segment may be brought selectivelyinto communication with each segment of the heat exchanger area (7; 107;207).
 2. A regenerative post-combustion apparatus as claimed in claim 1,in which the heat exchanger area is subdivided into n segments, whereina) the burn-out rotary slide valve (31; 131; 231) is subdivided into(n+1) segments, of which n are open in an upward and downward directionand one is open in an upward direction and closed in a downwarddirection; b) provided in the flow path between the burn-out rotaryslide valve (31; 131; 231) and the heat exchanger area (7; 107; 207) isa transfer area (41; 141; 241), which ba) at its top side is subdividedinto n sectors, which each enclose an angle of 360°/n and have athrough-opening (47), which communicates with one of the n segments ofthe heat exchanger area (7; 107; 207); bb) at its bottom side issubdivided into (n+1) sectors, which each enclose an angle of360°/(n+1), wherein n of said sectors have a through-opening (48), whichdepending on the rotational position of the burn-out rotary slide valve(31; 131; 231) may communicate with each of the latter's (n+1) segments,while one sector is closed and in a specific rotational position of theburn-out rotary slide valve (31; 131; 231) is positioned above thelatter's downwardly closed segment; bc) has n dividing walls (49), whichin part extend obliquely in such a manner from the top side to thebottom side of the transfer area (41; 141; 241) that the latter issubdivided into n segments, which at the top and bottom side each have athrough-opening (47, 48), wherein at least one of said segments at itsbottom side is delimited at least partially by the closed sector.
 3. Aregenerative post-combustion apparatus as claimed in claim 1, whereinthe burn-out rotary slide valve (31; 231) comprises a central tubularpiece (62; 262), the interior of which communicates via an opening (64)in its lateral surface with the downwardly closed segment of theburn-out rotary slide valve (31; 231).
 4. A regenerative post-combustionapparatus as claimed in claim 3, wherein the central tubular piece (65)of the burn-out rotary slide valve (31) is closed in a downwarddirection and communicates at the top with a coaxial central tubularpiece (66) of the above-lying component (41), which communicates withthe connection (68).
 5. A regenerative post-combustion apparatus asclaimed in claim 3, wherein the central tubular piece (265) of theburn-out rotary slide valve (231) is closed in an upward direction andcommunicates at the bottom with a coaxial central tubular piece (266) ofthe component (205) below, which communicates with the connection (268).6. A regenerative post-combustion apparatus as claimed in claim 1,wherein the downwardly closed segment of the burn-out rotary slide valve(131) has in its lateral surface an opening (121), via which itcommunicates with a stationary annular channel (122), which surroundsthe burn-out rotary slide valve (131) and in turn communicates with theconnection (168).